Intergranular segregation in Cu(Ag) and Ag(Cu) systems: Analysis of the driving force using a tight-binding scheme

Impurity segregation energy is studied for the grain boundary Sigma=5 (210)/[001] in Cu-Ag system in both dilute limits. We use N-body interatomic potentials derived from the second moment approximation of the tight-binding formalism. The aim of this work is to determine the driving force for intergranular segregation, by analogy with superficial segregation. We observe a site-to-site segregation reversal between the two systems, in agreement with the predominant role of the size effect. Moreover a collective relaxation mechanism is observed to accommodate the segregation on a plane non adjacent to the boundary plane.